1. Field of the Invention
The present invention relates generally to electrical switching apparatus and, more particularly, to a locking attachment for the handle of a circuit breaker.
2. Background Information
Electrical switching apparatus include, for example, circuit switching devices and circuit interrupters such as circuit breakers, contactors, motor starters, motor controllers and other load controllers.
Circuit breaker generally old and well known in the art. An example of a circuit breaker is disclosed in U.S. Pat. No. 5,341,191. Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit or fault condition. Molded case circuit breakers, for example, include at least one pair of separable contacts which are operated either manually by way of a handle disposed on the outside of the case or automatically by way of an internal trip unit in response to an overcurrent condition.
Circuit breakers typically have three possible operating handle positions, corresponding to the status of the separable contacts. For example, these positions may include an ON position, in which the separable contacts are closed, an OFF position in which the contacts are open, and a tripped position in which the contacts are tripped open. Typically, the handle position corresponding to the tripped position of the contacts is in between the ON and OFF positions.
In circuit breaker installations, for example in a panel board or load center, it is often desirable or essential that the settings of a single circuit breaker, or a group of circuit breakers, remain undisturbed. Unauthorized or inadvertent changing of the position of these breakers could result in annoying interruptions to service or operations, serious damage to an electrical apparatus, or even serious harm to a person. For example, accidental actuation of a circuit breaker might result in electrocution or shock to a workman performing electrical work or repair within an office building or home. Therefore, to prevent another person from inadvertently returning the circuit breaker handle to the ON position when a worker is doing electrical work in an area other than the immediate vicinity of the circuit breaker box or electrical panel, safety measures must be taken. One such safety measure is the addition of a locking mechanism to prevent displacement of the circuit breaker handle.
Although the main purpose of a circuit breaker is to trip during overload or short circuit conditions in order to protect downstream equipment and electrical wiring from damage, it may also be highly desirable to inhibit the circuit interruption function under certain conditions where, for example, the potential fire hazard of a non-opening circuit breaker is deemed to be a lesser hazard than if current flow to downstream devices is interrupted. The decision to accept the risk of fire over some other hazardous consequence may occur during emergencies or other critical situations where loss of life might occur if power is disrupted. Conceivable situations include, for example, circuit breakers employed in connection with combat (e.g., in a battleship under wartime conditions), fire-fighting (e.g., energizing pumps for pumping water to fire hoses in a high-rise building), spacecraft launch (e.g., energizing ground-based circuits critical to a safe launch), mining (e.g., energizing pumps employed to rapidly remove water from a flooded mine shaft), or nuclear power generation (e.g., energizing circuits critical to tripping a nuclear reactor). See, for example, U.S. Pat. No. 5,831,503. Although most circuit breakers can still trip internally even if the handle is held in the on position, a locking mechanism to prevent displacement of the circuit breaker handle would preclude manual operation that might inadvertently remove power in a critical situation.
U.S. Pat. Nos. 2,937,248 and 4,581,502 disclose a handle lock for a circuit breaker, which employs a bent piece of resilient wire material. A portion of the wire is inserted through a bore in the circuit breaker handle. The wire is then pivoted about the handle bore into a locking position within a recess in the switch housing.
U.S. Pat. Nos. 2,849,552; 3,408,466; 5,147,991; 5,219,070; 5,412,167; 5,500,495; 5,577,599; and 5,732,815 disclose handle locking mechanisms consisting of an assembly of at least two parts and each employs a padlock to lock the handle of the circuit breaker in a fixed position. Many known locking mechanisms of this type further employ a set or Allen screw to engage the circuit breaker handle, in order to prohibit its movement. See, e.g., U.S. Pat. Nos. 2,849,552; 5,147,991; 5,500,495; and 5,732,815.
U.S. Pat. No. 2,832,857 discloses a one-piece locking mechanism consisting of a metallic plate placed over the circuit breaker handle and locked into place by tangs which insert under the edge of the slot in the switch housing.
U.S. Pat. No. 4,435,624 discloses a lock off-lock on comprising a metal stamping that can be press fitted. A first handle-engaging portion, formed into a U-shaped structure, is inserted into an opening on the circuit breaker handle. A second handle-engaging portion is adapted to engage a surface of the handle adjacent to a dependent arcuate portion of the handle. A flat spring coupled to the side of the second handle engaging portion is engageable with the dependent arcuate portion and abuts the housing of the switch.
U.S. Pat. No. 6,160,227 discloses a retaining element for a toggle switch having a cylindrical rod-like extension inserted through a hole in the toggle switch and two arms adapted to interlock with a portion of the switch body and prevent displacement of the toggle.
There is room for improvement in locking mechanisms for electrical switching apparatus.
This need and others are satisfied by the invention, which is directed to a locking attachment for an electrical switching apparatus, which compressively captures an elongated operating member, and engages a housing in order to restrain movement of the operating member.
As one aspect of the invention, a locking attachment is used with an electrical switching apparatus, which includes a housing having an aperture with a first end and a second end, and also includes an elongated operating member protruding from the aperture, the elongated operating member moving between a first position proximate the first end of the aperture and a second position proximate the second end of the aperture, the locking attachment comprises: a locking member including a first end and a second end, the first end of the locking member having a compressive segment with opposed portions structured to compressively capture the elongated operating member between the opposed portions, the second end of the locking member structured to engage the housing at one of the first and second ends of the aperture, in order to restrain movement of the elongated operating member.
The elongated operating member may have an oblong shape with a first external portion positioned away from the aperture, and a second smaller external portion proximate the aperture. The first external portion of the oblong shape of the elongated operating member may have a first diameter, and the compressive segment of the locking member may have a capturing recess with a second diameter, which is smaller than the first diameter.
As another aspect of the invention, an electrical switching apparatus comprises: a housing including an opening having a first end and a second end; separable contacts; an operating mechanism including an elongated operating handle structured to open and close the separable contacts, the elongated operating handle protruding from the opening of the housing and moving between a first position proximate the first end of the opening and a second position proximate the second end of the opening; and a locking member including a first end and a second end, the first end of the locking member having a compressive segment with opposed portions structured to compressively capture the elongated operating handle between the opposed portions, the second end of the locking member structured to engage the housing at one of the first and second ends of the opening, in order to restrain movement of the elongated operating handle.
As another aspect of the invention, an electrical switching apparatus comprises: a housing including at least one opening having a first end and a second end; at least one pair of separable contacts; an operating mechanism including at least one elongated operating handle, each of the at least one elongated operating handles structured to open and close a corresponding pair of the at least one pair of separable contacts, each of the at least one elongated operating handle protruding from the at least one opening of the housing and moving between a first position proximate the first end of the at least one opening and a second position proximate the second end of the at least one opening; and a locking attachment comprising: a locking member including a first end and a second end, the first end of the locking member having a compressive segment with opposed portions structured to compressively capture one of the at least one elongated operating handle between the opposed portions, the second end of the locking member structured to engage the housing at one of the first and second ends of the at least one opening of the housing, in order to restrain movement of the one of the at least one elongated operating handle.